Although we have seen “morphing” structural materials before, they typically incorporate solenoids, pumps or motors that add weight and complexity. Now, however, scientists have developed a carbon fiber composite that shifts shape with a simple shot of electricity.
Created by a team at Sweden’s KTH Royal Institute of Technology, the three-layer solid-state material consists of two sheets of lithium ion-doped carbon fiber, between which is sandwiched a sheet of a solid electrolyte.
The latter is more specifically known as a “structural battery electrolyte,” and when a low-voltage DC current is run through it, ions migrate from one sheet of carbon fiber to the other (passing through the electrolyte). This causes the discharging layer of carbon to contract, while simultaneously causing the charging layer to expand. As a result, the entire piece of material bends to one side.
Even once the current is removed, the composite remains in this shape. If the current is reversed in a subsequent electrical charge, though, the lithium ions migrate in the opposite direction. Depending on the voltage, this causes the composite to bend back either to its neutral flat shape, or all the way over to the other side.
The material is lightweight, yet is also claimed to be stiffer than aluminum. Once developed further, it may find use in applications such as morphing airplane wings that don’t require ailerons, or wind turbine blades that alter their shape in order to achieve maximum efficiency in varying wind speeds.
“We have for some time worked with structural batteries, such as carbon fiber composites that also store energy like a lithium-ion battery,” says Prof. Dan Zenkert, co-author of a paper on the research. “Now we have further developed the work. We expect it lead to completely new concepts for materials that change shape only by electrical control, materials that are also light and rigid.”
The paper was recently published in the journal Proceedings of the National Academy of Sciences.
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